next-flight-css-loader - fix !=! support (#51115)

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### What?

- Use a `cssModules` option to configure the `next-flight-css-loader.ts`
based on the match resource.
- Added types
- Ran prettier

### Why?

NextJs supports css modules and global css files.
The `next-flight-css-loader.ts` is capable of dealing with both formats.

However under the hood the loader shares almost no code for css modules
and global css files.
To branch into the correct behaviour the `next-flight-css-loader.ts`
checks the extension of the file using
`this.resourcePath.match(/\.module\.(css|sass|scss)$/)`.

`this.resourcePath` does not include the information from webpacks `!=!`
import syntax.

One solution would be to use `this._module.matchResource` instead of
`this.resourcePath`.
But imho passing it from the webpack.config.js instead of duplicating
the css module file regexp felt cleaner.

### Further questions

- Should we update the loader banner comment?
- Can we drop `this.data.__checksum` in the pitch loader function for
css modules? (it would speed up css modules and for me it looks like it
isn't needed anymore for css modules because of
2eeb0c7
(4. April by @shuding)
- Should we split the loader into two loaders?

Fixes #52208

---------

Co-authored-by: Shu Ding <g@shud.in>

Author: jantimon

packages/next/src/build/webpack/config/blocks/css/index.ts

@@ -258,7 +258,14 @@ export const css = curry(async function css(
               test: regexCssModules,
               issuerLayer: APP_LAYER_RULE,
               use: [
-                require.resolve('../../../loaders/next-flight-css-loader'),
+                {
+                  loader: require.resolve(
+                    '../../../loaders/next-flight-css-loader'
+                  ),
+                  options: {
+                    cssModules: true,
+                  },
+                },
                 ...getCssModuleLoader(
                   { ...ctx, isAppDir: true },
                   lazyPostCSSInitializer
@@ -291,7 +298,14 @@ export const css = curry(async function css(
               test: regexSassModules,
               issuerLayer: APP_LAYER_RULE,
               use: [
-                require.resolve('../../../loaders/next-flight-css-loader'),
+                {
+                  loader: require.resolve(
+                    '../../../loaders/next-flight-css-loader'
+                  ),
+                  options: {
+                    cssModules: true,
+                  },
+                },
                 ...getCssModuleLoader(
                   { ...ctx, isAppDir: true },
                   lazyPostCSSInitializer,
@@ -338,7 +352,14 @@ export const css = curry(async function css(
                 sideEffects: true,
                 test: [regexCssGlobal, regexSassGlobal],
                 issuerLayer: APP_LAYER_RULE,
-                use: require.resolve('../../../loaders/next-flight-css-loader'),
+                use: {
+                  loader: require.resolve(
+                    '../../../loaders/next-flight-css-loader'
+                  ),
+                  options: {
+                    cssModules: false,
+                  },
+                },
               })
             : null,
           markRemovable({
@@ -389,7 +410,14 @@ export const css = curry(async function css(
                   test: regexCssGlobal,
                   issuerLayer: APP_LAYER_RULE,
                   use: [
-                    require.resolve('../../../loaders/next-flight-css-loader'),
+                    {
+                      loader: require.resolve(
+                        '../../../loaders/next-flight-css-loader'
+                      ),
+                      options: {
+                        cssModules: false,
+                      },
+                    },
                     ...getGlobalCssLoader(
                       { ...ctx, isAppDir: true },
                       lazyPostCSSInitializer
@@ -401,7 +429,14 @@ export const css = curry(async function css(
                   test: regexSassGlobal,
                   issuerLayer: APP_LAYER_RULE,
                   use: [
-                    require.resolve('../../../loaders/next-flight-css-loader'),
+                    {
+                      loader: require.resolve(
+                        '../../../loaders/next-flight-css-loader'
+                      ),
+                      options: {
+                        cssModules: false,
+                      },
+                    },
                     ...getGlobalCssLoader(
                       { ...ctx, isAppDir: true },
                       lazyPostCSSInitializer,

packages/next/src/build/webpack/loaders/next-flight-css-loader.ts

@@ -5,52 +5,56 @@
  */
 
 import crypto from 'crypto'
+import type webpack from 'webpack'
 
-export function pitch(this: any) {
-  if (process.env.NODE_ENV !== 'production') {
-    const content = this.fs.readFileSync(this.resourcePath)
-    this.data.__checksum = crypto
-      .createHash('sha256')
-      .update(typeof content === 'string' ? Buffer.from(content) : content)
-      .digest()
-      .toString('hex')
-  }
+type NextServerCSSLoaderOptions = {
+  cssModules: boolean
 }
 
-const NextServerCSSLoader = function (this: any, content: string) {
-  this.cacheable && this.cacheable()
-
-  // Only add the checksum during development.
-  if (process.env.NODE_ENV !== 'production') {
-    const isCSSModule = this.resourcePath.match(/\.module\.(css|sass|scss)$/)
-    const checksum = crypto
-      .createHash('sha256')
-      .update(
-        this.data.__checksum +
-          (typeof content === 'string' ? Buffer.from(content) : content)
-      )
-      .digest()
-      .toString('hex')
-      .substring(0, 12)
-
-    if (isCSSModule) {
-      return `\
+const NextServerCSSLoader: webpack.LoaderDefinitionFunction<NextServerCSSLoaderOptions> =
+  function (content) {
+    this.cacheable && this.cacheable()
+    const options = this.getOptions()
+    let isCSSModule = options.cssModules
+
+    // Only add the checksum during development.
+    if (process.env.NODE_ENV !== 'production') {
+      // This check is only for backwards compatibility.
+      // TODO: Remove this in the next major version (next 14)
+      if (isCSSModule === undefined) {
+        this.emitWarning(
+          new Error(
+            "No 'cssModules' option was found for the next-flight-css-loader plugin."
+          )
+        )
+        isCSSModule =
+          this.resourcePath.match(/\.module\.(css|sass|scss)$/) !== null
+      }
+      const checksum = crypto
+        .createHash('sha256')
+        .update(typeof content === 'string' ? Buffer.from(content) : content)
+        .digest()
+        .toString('hex')
+        .substring(0, 12)
+
+      if (isCSSModule) {
+        return `\
 ${content}
 module.exports.__checksum = ${JSON.stringify(checksum)}
 `
-    }
+      }
 
-    // Server CSS imports are always available for HMR, so we attach
-    // `module.hot.accept()` to the generated module.
-    const hmrCode = 'if (module.hot) { module.hot.accept() }'
+      // Server CSS imports are always available for HMR, so we attach
+      // `module.hot.accept()` to the generated module.
+      const hmrCode = 'if (module.hot) { module.hot.accept() }'
 
-    return `\
+      return `\
 export default ${JSON.stringify(checksum)}
 ${hmrCode}
 `
-  }
+    }
 
-  return content
-}
+    return content
+  }
 
 export default NextServerCSSLoader